[ExeFS] LZ77 decompression for .code file

CMakeLists.txt

@@ -70,6 +70,7 @@ set(HEADER_FILES include/emulator.hpp include/helpers.hpp include/opengl.hpp inc
                  include/PICA/gpu.hpp include/PICA/regs.hpp include/services/ndm.hpp
                  include/PICA/shader.hpp include/PICA/shader_unit.hpp include/PICA/float_types.hpp
                  include/logger.hpp include/loader/ncch.hpp include/loader/ncsd.hpp include/io_file.hpp
+                 include/loader/lz77.hpp
 )
 
 set(THIRD_PARTY_SOURCE_FILES third_party/imgui/imgui.cpp

include/loader/lz77.hpp

@@ -0,0 +1,88 @@
+#pragma once
+#include <algorithm>
+#include <vector>
+#include "helpers.hpp"
+
+// For parsing the LZ77 format used for compressing the .code file in the ExeFS
+namespace CartLZ77 {
+    // The difference in size between the compressed and decompressed file is stored
+    // As a footer in the compressed file. To get the decompressed size, we extract the diff
+    // And add it to the compressed size
+    static u32 decompressedSize(const u8* buffer, u32 compressedSize) {
+        u32 sizeDiff;
+        std::memcpy(&sizeDiff, buffer + compressedSize - 4, sizeof(u32));
+        return sizeDiff + compressedSize;
+    }
+
+    template <typename T>
+    static u32 decompressedSize(const std::vector<T>& buffer) {
+        return decompressedSize((u8*)buffer.data(), u32(buffer.size() * sizeof(T)));
+    }
+
+    static bool decompress(std::vector<u8>& output, const std::vector<u8>& input) {
+        u32 sizeCompressed = input.size() * sizeof(u8);
+        u32 sizeDecompressed = decompressedSize(input);
+        output.resize(sizeDecompressed);
+
+        const u8* compressed = (u8*)input.data();
+        const u8* footer = compressed + sizeCompressed - 8;
+
+        u32 bufferTopAndBottom;
+        std::memcpy(&bufferTopAndBottom, footer, sizeof(u32));
+
+        u32 out = sizeDecompressed; // TODO: Is this meant to be u32 or s32?
+        u32 index = sizeCompressed - ((bufferTopAndBottom >> 24) & 0xff);
+        u32 stopIndex = sizeCompressed - (bufferTopAndBottom & 0xffffff);
+
+        // Set all of the decompressed buffer to 0 and copy the compressed buffer to the start of it
+        std::fill(output.begin(), output.end(), 0);
+        std::copy(input.begin(), input.end(), output.begin());
+
+        while (index > stopIndex) {
+            u8 control = compressed[--index];
+
+            for (uint i = 0; i < 8; i++) {
+                if (index <= stopIndex)
+                    break;
+                if (index <= 0)
+                    break;
+                if (out <= 0)
+                    break;
+
+                if (control & 0x80) {
+                    // Check if compression is out of bounds
+                    if (index < 2)
+                        return false;
+                    index -= 2;
+
+                    u32 segmentOffset = compressed[index] | (compressed[index + 1] << 8);
+                    u32 segment_size = ((segmentOffset >> 12) & 15) + 3;
+                    segmentOffset &= 0x0FFF;
+                    segmentOffset += 2;
+
+                    // Check if compression is out of bounds
+                    if (out < segment_size)
+                        return false;
+
+                    for (uint j = 0; j < segment_size; j++) {
+                        // Check if compression is out of bounds
+                        if (out + segmentOffset >= sizeDecompressed)
+                            return false;
+
+                        u8 data = output[out + segmentOffset];
+                        output[--out] = data;
+                    }
+                }
+                else {
+                    // Check if compression is out of bounds
+                    if (out < 1)
+                        return false;
+                    output[--out] = compressed[--index];
+                }
+                control <<= 1;
+            }
+        }
+
+        return true;
+    }
+}

src/core/loader/ncch.cpp

@@ -1,4 +1,5 @@
 #include <vector>
+#include "loader/lz77.hpp"
 #include "loader/ncch.hpp"
 #include "memory.hpp"
 
@@ -68,8 +69,8 @@ bool NCCH::loadFromHeader(u8* header, IOFile& file) {
         }
 
         // ExeFS format allows up to 10 files
-        for (int file = 0; file < 10; file++) {
-            u8* fileInfo = &exeFSHeader[file * 16];
+        for (int i = 0; i < 10; i++) {
+            u8* fileInfo = &exeFSHeader[i * 16];
 
             char name[9];
             std::memcpy(name, fileInfo, 8); // Get file name as a string
@@ -79,15 +80,30 @@ bool NCCH::loadFromHeader(u8* header, IOFile& file) {
             u32 fileSize = *(u32*)&fileInfo[0xC];
 
             if (fileSize != 0) {
-                printf("File %d. Name: %s, Size: %08X, Offset: %08X\n", file, name, fileSize, fileOffset);
+                printf("File %d. Name: %s, Size: %08X, Offset: %08X\n", i, name, fileSize, fileOffset);
             }
 
             if (std::strcmp(name, ".code") == 0) {
-                std::vector<u8> buff;
+                std::vector<u8> code;
 
                 if (compressCode) {
-                    //Helpers::panic("Compressed .code file!");
+                    std::vector<u8> tmp;
+                    tmp.resize(fileSize);
+
+                    // A file offset of 0 means our file is located right after the ExeFS header
+                    // So in the ROM, files are located at (file offset + exeFS offset + exeFS header size)
+                    file.seek(exeFSOffset + exeFSHeaderSize + fileOffset); 
+                    file.readBytes(tmp.data(), fileSize);
+                    
+                    // Decompress .code file from the tmp vector to the "code" vector
+                    if (!CartLZ77::decompress(code, tmp)) {
+                        printf("Failed to decompress .code file\n");
+                        return false;
+                    }
                 } else {
+                    code.resize(fileSize);
+                    file.seek(exeFSOffset + exeFSHeaderSize + fileOffset);
+                    file.readBytes(code.data(), fileSize);
                     Helpers::panic("Uncompressed .code file!");
                 }
             }